Abstract: The pressure-induced structural phase transition of XeO₃ is studied by first principle calculations. The transition from P2₁2₁2₁ to Pnma accompanied by a drastic reduction of volume is found at 2.18 GPa. The symmetrilized Xe–O₂ bonds give rise to the better symmetry of high pressure phase. O-hopping between different possible local minima and the motion of Xe along the y axis may be responsible for phase transition. Results of electron localization function indicate that three ipsilateral Xe–O bonds lead to a lone-pair contour of Xe⁶⁺.